This invention relates to a system for detecting high temperature areas or "hot spots" on either stationary vanes or rotating blades of a combustion turbine.
As will be appreciated by one skilled in the art, a turbine generally has a rotor, rotating blades affixed to the rotor, stationary vanes affixed to an outer cylinder of the turbine, an inlet for in taking a hot fluid and an outlet for exhausting the fluid. The hot fluid, which is usually either steam or gas, flows into the intake, over the exterior of the rotating blades and stationary vanes and through the outlet. As the fluid flows through the turbine, it drives the rotating blades. Since the rotating blades are connected to the rotor, as they rotate the rotor also rotates.
In order to increase the efficiency of turbines, they are currently being designed to operate at such high temperatures that the vanes and blades of a turbine must be cooled to prevent thermal damage. Potentially, "hot spots" (localized areas of high temperature) in a portion of a vane or blade can occur as the hot fluid flows over their exterior. Currently, in "closed-loop" cooling systems the blades or vanes are cooled by sending a cooling medium through their interior. Additionally, the vanes and blades are protected from heat associated with these high temperatures by a thin thermal barrier coating (TBC) applied to their exterior. This thin thermal barrier coating provides a layer of insulation to reduce or minimize heat transfer from the hot gas to the vanes or blades. This prevents hot spots from developing. If a hot spot develops, the TBC will be expelled from the vane or blade and it will be exposed to the hot gas. Exposure to the hot gas can cause a vane or blade to reach high temperatures and to suffer thermal damage.
In order to determine if a vane or blade has reached a high temperature, the temperature of each of the vanes and blades is monitored. One method of monitoring the temperatures of the vanes and blades includes intrusive monitoring. For example, temperature detectors such as thermocouples or resistance temperature detectors (RTDS) can be placed in the turbine to monitor the temperature of the vanes and blades at various locations. Intrusive monitoring however, has a significant disadvantage; it does not monitor the temperature along the entire surface of a vane or blade. Rather, it merely monitors the temperature at discrete locations.
Monitoring the temperature over the entire surface of turbine components, such as a vane or blade, is particularly important because these components are designed to have a relatively even temperature distribution. As will be appreciated by those skilled in the art, turbine components are designed to have an even temperature distribution in order to reduce the emission of nitrogen oxide (NOX). Therefore, the likelihood that a specific location will reach a hot spot is not significantly different than the likelihood of another location becoming relatively hot. Consequently, with an intrusive temperature monitoring system a component may reach an excessive temperature in a region not directly monitored by a temperature detector. If this occurs, the TBC could breakdown and a vane or blade could be damaged. Due to the relatively large and complex nature of the blades and vanes, their support structures and other aspects of a turbine, it is impracticable to provide a global system of detection (one that monitors the temperature over the entire surface of the components) with an intrusive monitoring technique. Thus, an improved temperature detection system is needed that monitors the temperature over the entire surface of a vane or blade.